Outbound Calls from an IP Phone Through a SIP Trunk to the PSTN Fails with a Fast Busy Tone

Unanswered Question
Apr 27th, 2010

while ticking the MTP option in sip trunk the highlighted issue raises

does any one know how to play with this issue

call manager version is 6.0.1

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Aaron Harrison Tue, 04/27/2010 - 23:47


The MTP is a service that runs on your CallManager server (the IP Voice Media Streaming Service).

It is assigned from either the unassigned pool (if you have not put each MTP in at least on Media Resource Group) or it is assigned from the MRGL of the device that requires the MTP (i.e. the trunk).


1) Ensure that you have an MRGL assigned to the trunk which contains an MRG with at least one MTP service.

2) Make sure that MTP service is in an appropriately configured device pool

3) Make sure that the traffic to the trunk is using G711, as G729 is not supported with the software MTP on CallManager

4) If you must use G729, then you will need to provision a hardware/gateway based transcoder which can also act as an MTP, but will support G729.



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bilalsheikh Wed, 04/28/2010 - 02:54

How to check that traffic to trunk is G711/729. Rest of the configuration i have checked that seems to be O.K


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